PATTANI, Thailand (Reuters) - Suspected Muslim rebels in southern Thailand killed three soldiers and a district election official in a bomb attack on Sunday as a general election was being held around the country.

Police said the violence was not related to the election that has divided Thailand, with anti-government protesters and the main opposition Democrat Party opposing the vote.

Jatra Promkaew, an election official in Pattani province, was killed along with three soldiers after gunmen fired shots at a security checkpoint and set off three bombs, police said.

"Four people died in an attack carried out by a group of around 20 insurgents," Pattani chief of police Phot Suaysuwan told Reuters. "The attack was related to ongoing violence in the southern provinces and unrelated to the election."

Thailand went to vote under heavy security on Sunday in an election that could push the country deeper into political turmoil.

Ten people have died and at least 577 have been wounded in politically related violence since late November.

Voting was going smoothly in the predominantly Muslim southern provinces of Pattani, Yala and Narathiwat, said national security chief Paradorn Pattanathabutr.

Thailand is a mainly Buddhist country and resistance to central government rule in the Muslim-majority provinces has existed for decades, resurfacing violently in 2004.

The opening of peace talks with rebel groups last year has done nothing to end violence in the south, where more than 5,700 people have died since January 2004.

The three provinces were once part of a Malay Muslim sultanate before being annexed by Thailand in 1909. Muslims in the area largely oppose the presence of tens of thousands of soldiers and armed Buddhist guards in the region.

KABUL (Reuters) - Presidential candidates in Afghanistan begin two months of campaigning on Sunday for an election that Western allies hope will consolidate fragile stability as their forces prepare to leave after nearly 13 years of inconclusive war.

The Taliban have rejected the April 5 election and have already stepped up attacks to sabotage it. The militants will also be looking to capitalise if the vote is marred by rigging and feuding between rivals seeking to replace President Hamid Karzai, who can not run for a third term under Afghan law.

Whoever replaces him will inherit a country beset by deepening anxiety about security as most foreign troops prepare to pull out by the end of the year, leaving Afghan forces largely on their own to battle the insurgency.

Monthly attacks in the capital, Kabul, where candidates are expect to focus their efforts to win over women and young people, are at the highest since 2008, one embassy said in a recent confidential security report.

"This increase can be attributed to efforts towards the presidential elections," the embassy said.

Many Afghans say they are taking precautions.

"I have already advised my family to cut down unnecessary travel and never attend any big meetings," said Fawad Saleh, a barber in the Shar-e Naw area of Kabul. "The Taliban will reach any campaign and they will react violently."

While Afghanistan has no majority community, ethnic Pashtuns are considered the largest community and ethnicity will play a big role in deciding the next president.

Western diplomats expect the first round to be split between one of several prominent Pashtuns and former foreign minister Abdullah Abdullah, an ethnic Tajik who appeals to that voter base and who was Karzai's main challenger in the last election in 2009.

Two of Abdullah's campaigners in western Herat province were shot dead in their car on Saturday, police officials said, in another grim pointer to the violence ahead.

CAMPAIGN BRINGS HOPE

The most ambitious efforts to conduct opinion polls, which were funded by the United States, have been cancelled over accusations Washington was seeking to manipulate the outcome.

But a first set of polling results in December put Western-leaning intellectual and ethnic Pashtun former finance minister Ashraf Ghani in the lead ahead of Abdullah.

In spite of the threat of Taliban attacks, the campaigning season will kick off on Sunday with the rival camps throwing lavish parties in Kabul hotels.

Afghan businessmen have welcomed the campaign as a signal the political process is moving forward. Uncertainty about the future helped drive a tumble of more than 10 percent in economic growth in 2013, according to the World Bank.

"Now there is a hope for me and for the people of Afghanistan," said Ismail Temorzada, who owns a carpet shop on Kabul's once busy Chicken Street. His last sale was eight months ago, he said.

But optimism remains clouded by Karzai's refusal to sign a bilateral deal to let a contingent of U.S. troops stay after 2014. If Washington pulls all of its troops, much of the aid that pays for most government and security is likely to dry up.

Widespread ballot-stuffing and wrangling marred the 2009 vote. Afghanistan's backers hope a country split along ethnic lines can accept the outcome as legitimate this time, even if the winner is not from the biggest community.

"The Pashtuns believe they have the right to the presidency because they are the most, and that's not good," said one Western diplomat.

(Additional reporting by Mirwais Harooni; Writing by Jessica Donati; Editing by Maria Golovnina and Robert Birsel)

BANGKOK (Reuters) - Thailand went to the polls under heavy security on Sunday in an election that could push the divided country deeper into political turmoil and leave the winner paralysed for months by street protests, legal challenges and legislative limbo.

Voting started peacefully a day after seven people were wounded by gunshots and explosions during a clash between supporters and opponents of embattled Prime Minister Yingluck Shinawatra in a north Bangkok stronghold of her Puea Thai Party.

Voting was called off in the district and some other polling stations were unable to open because of pressure by anti-government protesters. Polling outside the capital and the south was unaffected.

"The situation overall is calm and we haven't received any reports of violence this morning," National Security Council chief Paradorn Pattanatabutr told Reuters. "The protesters are rallying peacefully to show their opposition to this election."

The usual campaign billboards, glossy posters and pre-election buzz have been notably absent, as will be millions of voters fearful of violence or bent on rejecting a ballot bound to re-elect the political juggernaut controlled by Yingluck's billionaire brother, Thaksin Shinawatra.

Thaksin, 64, is loved and loathed in Thailand, but his parties have won every poll since 2001. His opponents say he is a corrupt crony capitalist who rules by proxy from self-exile in Dubai.

"We're not blocking the election. We're postponing it," said Nipon Kaewsook, 42, one of the hundreds of protesters blocking Ratchathewi District Office in central Bangkok to prevent the distribution of dozens of ballot boxes.

"We still need an election, but we need reform first," added Nipon, an English teacher from Phattalung in southern Thailand.

Protesters shouted "Yingluck get out!" and "Thaksin go to jail!" They took celebratory selfies in front of the ballot boxes, placed in a car park at the back of the building.

Victory celebrations for Yingluck would probably be muted. With parliamentary seats unable to be filled, she could find herself on shaky ground, exposed to legal attacks and unable to pass bills and budgets crucial to reviving a stuttering economy.

Yingluck last week refused to postpone the election, even though a fifth of those registered for advance voting were unable to cast ballots after protesters blocked polling stations in 49 of 50 Bangkok districts as part of a "shutdown" of key intersections. In 28 southern constituencies, no votes will be cast because no candidates could sign up.

The Election Commission says results will not be available on Sunday. Its commissioners are braced for a deluge of complaints and challenges to the results.

"There's been a lot of obstruction, so much, every single step of the way," commission secretary-general Puchong Nutrawong told Reuters.

"We don't want this election to be a bloody election. We can get every single agency involved to make this election happen, but if there's bloodshed, what's the point?"

INTRACTABLE CRISIS

Anti-government demonstrators say Thaksin subverted Thailand's fragile democracy by entrenching money politics and using taxpayers' money for generous subsidies, cheap healthcare and easy loans that have bought him loyalty from millions of working-class Thai voters in the north and northeast.

With broad support from Bangkok's middle class and tacit backing of the royalist establishment, old-money elite and military, the protesters reject the election and want to suspend democracy, replacing it with an appointed "people's council" to reform politics and erode Thaksin's influence.

The latest round of tumult in the eight-year political conflict erupted in November and underscored Thaksin's central role in the intractable struggle, both as hero and villain.

Yingluck was largely tolerated by Thaksin's opponents but her party miscalculated when it tried to introduce a blanket amnesty that would have nullified a graft conviction against Thaksin and allowed him to return home.

Many Thais see history repeating itself after a cycle of elections, protests and military or judicial interventions that have polarised the country and angered Thaksin's "red shirt" supporters, who held crippling blockades in 2010 and have vowed to defend his sister from any overthrow attempt.

Thailand's military has remained neutral so far, but the judiciary has taken on an unusually large number of cases in the past two months in response to complaints against Yingluck and Puea Thai that could result in the party's dissolution and lengthy bans for its top politicians.

There is also a chance the election could be annulled, as it was in 2006, over a technicality. The Election Commission is expecting lawsuits to be filed demanding the election be voided.

The main opposition Democrat Party is boycotting the poll and the commission has already voiced concerns that it would result in too few legitimately elected MPs to form a parliamentary quorum.

With no quorum to re-elect a prime minister, it looks likely Yingluck could be a caretaker premier for months. Even with a fresh mandate, a stalemate is almost certain, giving her opponents more time to intensify their campaign against her and for legal challenges to be lodged.